1. Field of the Invention
The subject matter of this disclosure relates to data communications and, more particularly, to signal transmission in point-to-point radio systems.
2. Description of the Related Art
As the need for the transmission of voice, video, and data have constantly escalated with the increasing use of wireless access devices, the importance of maximizing the utilization of radio frequency (RF) spectrum has increased sharply. For licensed band point-to-point systems, combinations of mechanisms have been employed to increase available data rates. Two principal philosophies can be employed: (1) Increase the number of data bits sent per Hz of bandwidth (b/Hz), or (2) increase the amount of bandwidth (Hz) used.
Increases in the b/Hz rate have been constantly growing through improving digital processing techniques and improved analog fidelity in the analog RF circuits, and increases in the bandwidth have increased to a limited extent by using wider licensed bandwidths, by using both horizontal and vertical polarizations along with digital processing techniques (cross polarization interference cancellation or “XPIC”). The most aggressive techniques employ both.
However, existing systems implementing these techniques incorporate filters, diplexers, couplers, Ortho-Mode Transducer (OMT), and/or other elements that lead to signal loss and degradation of signals, higher costs, more weight, increased complexity, constraints on transmission range of components, and additional design problems. Accordingly, there is a need for a point-to-point communication radio system that avoids the cost, electrical losses, weight, tuning range limitations, and parametric limitations associated with the filters, diplexers, couplers, and OMT combining networks of present systems.